1. Field of the Invention
The present invention concerns automated computerized control systems for the speed, acceleration, and/or trim control of power boats, typically small pleasure boats.
The present invention further concerns computerized electronic safety systems for interacting with a human boat operator for sequencing activities during trailering, hauling out, launching, starting, and like events during the deployment, use, and recovery of small power watercraft.
The present invention further concerns an economical inclinometer/accelerometer that is interrogatable by electrical means including digital computers, and suitable for incorporation in a boat's electrical system, particularly the electrical system of a small power boat.
2.0 Requirements for Speed Control in Operation of Power Boats
A speed, or cruise control is equally as useful during cruising over distances in a power boat as it is useful in driving over distances in an automobile. It may be more useful because power boats are, in some waterways, less prone to encounter circumstances which require variation from a preset speed than are automobiles traveling upon roadways.
An additional requirement for speed control of power boats arises upon the use of such boats for water skiing. Water skiers generally have individually preferred speeds for skiing. If the skier is to be comfortable, these speeds must be controlled within a narrow range, typically within .+-.0.5 miles per hour. Additionally, water skiers participating in competition water skiing, especially slalom water skiing, must generally run a ski course at an identical predetermined speed, as is dictated by the rules of the sport. There is a corresponding requirement that the speed of the power boat pulling a water skier should be controllable at high precision and repeatability.
2.1 Requirements for Power Boat Acceleration Control
Control of the acceleration of a power boat is important during the use of such boat for pulling water skiers. The pulling of a water skier from an in-water position to a skiing position requires the skier to position himself/herself in the water with ski tips upwards and tilted forward at an approximate 30-45' angle, arms outstretched forwards, and ski rope taut. When ready, the water skier signals the power boat driver to start. The driver normally must apply considerable throttle, often full throttle, to pull the skier from the water and up to the desired water skiing speed. However, for heavy body weight skiers, or skiers behind boats having powerful engines and fast accelerations, a full throttle acceleration may produce far too much force for the skier to be able to hold on to the tow rope and begin water skiing. There is even a risk that high initial acceleration can cause physical harm to the arms and shoulder joints of the skier. Operators of powerful ski boats typically attempt to solve this problem by controlling how fast they move the throttle forward during the course of initiating water skiing.
This is generally an imperfect solution, especially by amateur boat drivers who are unskilled or unpracticed at towing water skiers. Irregular and inconsistent acceleration of the boat magnifies false starts by the water skier and generally detracts from the pleasure of water skiing. Inconsistent acceleration of the boat also makes it more difficult for beginning water skiers to learn how to be pulled from the water to the water skiing position.
There correspondingly exists a requirement for controlling the acceleration of a power boat, particularly as used for pulling water skiers.
2.2 Requirements for Power Boat Trim Control
Trim is the adjustment of a power boat's propulsion system, commonly a propeller, so that it runs at the most efficient angle with respect to the surface of the water even though the hull of the boat may assume different angles relative to such water surface. For example, a power boat may be planing on the surface of the water at an appreciable angle to the surface.
A control of power boat trim that maintains the force generated by the boat's propulsion to be perpendicular to the surface of the water is optimal for (i) maximizing the forward thrust provided to the boat in the water, (ii) increasing the speed with which the boat will operate at a given throttle setting, and (iii) improving fuel economy. Trim control is also useful in a small power boat during the pulling of water skiers. Proper trim adjustment promotes smooth transitions of the power boat between its operational ranges. Skiing behind a power boat that puts out a regular, and regularly progressive, wake due to trim control is especially beneficial when such wake is used by water skiers to facilitate the performance of acrobatics, such as jumps.
Finally, a power boat that is controlled in trim exhibits handling and ride comfort that is strongly preferred by some owners. Severe hull angles are readily induced in small outboard boats under high acceleration, often by youthful operators. Mature power boat owner/operators commonly prefer a smoother ride. Additionally, some power boats are operated in high sea states. Trim control promotes a smooth ride and/or reduction of boat motion due to sea state condition.
2.3.1 Previous Manual and Automatic Trim Control Systems
Manual and automatic trim control for marine drives such as outboards and stern drives are known in the art. A hydraulic cylinder arrangement is disclosed in U.S. Pat. No. 3,434,449 to I. W. North. The cylinder is used to trim a drive unit during operation of a power boat, and additionally to tilt the drive unit for beaching or trailering of the boat. The control of the trim is accomplished through manually operated switches in order to move the drive to the desired trim position.
Because of the limitations of such a manual trim control system wherein the operator must be attentive in order to maintain a proper boat attitude under varied boat loading and speed conditions, automated trim control systems were developed U.S. Pat. No. 4,318,699 to Wenstadt et al., shows a marine trim control system that senses an off-plane and an on-plane condition of a power boat. Responsively to this sensing the trim control system automatically positions a trimmable drive for desired boating operation. The control may alternatively position the drive at one or more trim positions in response to one or more sensed operating speeds. For example, the trim position may be set in response to sensed fluid pressure opposing the movement of the power boat, or alternatively, in response to the sensed engine speed.
It is not completely satisfactory to control the trim of a power boat in response to either its planing condition, its engine speed, or its speed through the water. Effectively, both planing and engine speed and hull speed indications all represent secondary information concerning the attitude that the boat's propulsion system has probably assumed. The trim control system is calibrated for a particular boat, for a particular loading and load distribution of this boat, for a particular sea state and for a particular trim control system.
Unfortunately, in the real world the variables associated with power boat propulsion do not remain constant. The inclination of a boat hull and the optimal trim of the boat's propulsion at any particular engine speed may be a function of the hull shape and cleanliness. The inclination of a boat hull and the trim of the boat's propulsion at any particular hull speed may be a function of the boat's load and load distribution. The trim control of the propulsion system itself may exhibit differing trim angle responses to the same control inputs (drive signals) dependent upon seas state, wear, temperature and other factors.
Even if all variables remain as they were during calibration of an individual system, knowledge of engine or hull speed does not necessarily permit extrapolation of the probable current uncompensated trim angle, and application of the appropriate trim angle correction that is calculated to return trim angle to optimal. It has been found by actual observation of the inventor that, depending upon the position of the people and cargo in a power boat, the angle of the boat in the water at rest can vary between 0 and 8 degrees. In one particular boat, it was found that the inclination angle with only two people in the boat was +4 degrees off the horizon. This angle means that the boat floor is oriented relative to level with the bow up at a 4 degree angle. If most of the weight of passengers were moved to the front of the boat, it was possible with this particular boat to get the inclination angle down to 0 degrees. With most of the weight in the back the inclination angle would come up to +8 degrees.
When the same particular small boat was accelerated, the angle the boat took with the water varied from +15 to +25 degrees. The particular boat started out fairly level and went through a steep inclination angle as it approached the planing condition. When the boat reached a plane, its nose dropped down and it assumed an inclination angle approximately +1 or +2 degrees greater than the rest position. From loading the boat differently along the bow to stern axis it was found that the inclination angle on plane varied from about +2 to +8 degrees. During the time that the boat is coming up on plane, it is clearly accelerating. After it gets on plane it assumes an angle very close to the angle that it was at when it was at rest. In fact, depending upon load conditions in the boat, the two angles were determined to overlap each other. Accordingly, there is no window allowing one to clearly differentiate between the at rest position and on plane condition. The present invention will be found to offer a way around this difficulty.
Recalling that the primary goal of trim control is to optimally position the boat's propulsion relative to the surface of the water, the physical variable which would logically be sensed in order to control trim of a power boat would be the inclination of the boat's hull. Possibly the reason that inclination has not been sensed in prior power boat trim control systems is that inclinometers feasible of incorporation into such systems are generally expensive, unreliable, and difficult to maintain in the high vibration and corrosive marine environment of a small power boat.
2.4 Prior Accelerometers and Inclinometers
The existing art regarding inclinometer and accelerometers is of importance relative to one aspect of the present invention. One previous inclinometer and accelerometer is the pendulous inclinometer/accelerometer. In this device a pendulous mass is suspended to pivot in one or more axes of freedom. The motion of the pendulous mass is subject to the gravitational forces as well as to the acceleration forces. Consequently, a pendulous inclinometer/accelerometer serves to sense both inclination and acceleration, and will sense a net force which is the vector combination of both the inclination and acceleration forces.
The motion of the pendulum of a pendulous inclinometer/accelerometer may be detected and may be used to generate a display that is indicative of inclination and acceleration. Normally the motion detection transpires along each of a plurality of orthogonal axes.
In pendulous inclinometers/accelerometers exhibiting quick and accurate response, it is of considerable importance that the pendulous mass should experience low friction to its movement. One prior electrical scheme for detecting the position of the pendulous mass with minimal restriction or friction upon its motional freedom is to emit a light beam radially from the end of the pendulous mass. This light beam travels through space and intercepts a spatially extended array of light detectors disposed oppositely to the light-emitting end of the pendulum. The position of the pendulum can thereby be determined with no mechanical resistance.
These and other prior schemes for electrically interrogatable inclinometers/accelerometers generally make these instruments both expensive and delicate. Conversely, it is known that a simple fluid-filled arculate tube can serve as an indication of inclination or acceleration. Such tubes are commonly used aboard major nautical vessels to provide a visual indication to the operators of the vessel as to whether the vessel is being operated at attitudes that are within its prescribed design limits. The visually indicating inclinometer/accelerometer displaying colored fluid within a transparent tube does not, however, commonly offer an electrical interface.
Accordingly, it would be useful if an economical, ruggedized, low maintenance, inclinometer/accelerometer that is directly incorporatable within, and interrogatable by, an electrical control system could be constructed.
2.5 Requirements for a Power Boat Safety and Operational Status Surveillance System
Operation of a power boat, especially a small pleasure craft used primarily for recreation, is both deceivingly easy and unforgiving of mistakes.
The trailering, launching from a land trailer into water, and recovery sequences of a trailerable power boat are each quite complex. Many lines and straps must be selectively attached and unattached, boat engine operation and trim angle must be controlled, and the boat's bilge must be sealed while within the water but vented on land.
During operation the trim should be monitored to be appropriate (especially when starting in shallow water), and the engine compartment should not be permitted to accumulate explosive vapors.
On a large ship specialists and special systems in propulsion, cargo distribution, line handling and/or safety monitor the ship's function. For small power boats the operation, and safety of the boat is left to the skill and memory of the operator and his/her generally small crew. Because of the often amateur status of these operators and/or crew, their inattentiveness or forgetfulness, or their ignorance the more complex sequences of small boat handling may become a comedy of errors. It is a rare marina where the boat launch ramps are not scarred with props dragged against the ramp surface during recovery of trailerable power craft with improper adjustment of the craft's trim, or where operators have not scrambled to replace a bilge plug in a boat just launched with its bilge unsealed to the water. Many less major errors likewise detract from the enjoyment, economy, safety and professionalism of power boating.
It would correspondingly be desirable if some nature of a man-machine system could facilitate correct power boat operation and safety, especially by parties that exhibit poor skills in these areas.